After updating my Windows computer, I can no longer type the left square bracket character ([) using my physical keyboard. The right bracket (]) and every other key work normally. The recent updates were the August 2026 .NET Framework Security Update (KB5120710), August 2026 Security Update (KB5121003, build 26100.9168), and the Windows Malicious Software Removal Tool x64 update (KB890830). Could one of these updates be responsible, and how can I troubleshoot the problem or roll back an update if necessary?
3 Answers
This sounds more like a coincidental problem with the keyboard or a single key switch than an issue caused by Windows Update. You can uninstall the recent updates to test the theory, but I wouldn’t expect that to fix a physical key failure.
You can check Settings > Windows Update > Update history > Uninstall updates. Remove the recent updates one at a time and test the key after each removal. If the key still fails while the on-screen keyboard works, the update probably isn’t the cause.
Try launching the Windows On-Screen Keyboard by pressing Win+R, entering osk.exe, and pressing Enter. If the left bracket works there, Windows can produce the character and the problem is probably limited to the physical keyboard, its connection, or the keyboard layout.
The left bracket does work with the on-screen keyboard. I also replugged the physical keyboard and confirmed that its drivers are up to date, so I’m testing whether uninstalling the recent updates changes anything.